Program Director/Principal Investigator (Last, First, Middle): Vyavahare Narendra R. Project Summary Traumatic brain injury (TBI) initiates a complex physiological response involving both progressive tissue damage and activation of reparative processes including neurogenesis, angiogenesis, and plasticity through axonal sprouting and synaptic reorganization. The limited capacity for remodeling in the adult brain is attributable to age-related changes in the extrinsic neuronal microenvironment such as accumulation of myelin- associated inhibitors (MAIs), and chondroitin sulfate proteoglycans (CSPGs), as well as intrinsic changes in neuronal biochemistry such as cyclic AMP (cAMP) levels. Several groups have begun to investigate therapeutic strategies to overcome these barriers using monoclonal antibodies against MAIs, CSPG- degradative enzymes, and drugs that modulate cAMP levels. Despite encouraging results, the clinical translation of these approaches is limited by the need for invasive delivery methods, transplantation of xenogenic cells, and use of bacterially-derived enzymes. The objective of this project is to develop novel neuron-specific nanotherapeutics for combinatorial delivery of drug and small interfering RNA (siRNA) targeting both extrinsic and intrinsic barriers to neuroplasticity. These nanotherapeutics will consist of poly (lactide-co-glycolide)-graft-polyethyleneimine (PgP) copolymer micelles loaded with 1) rolipram, phosphodiesterase inhibitor in the hydrophobic core to stabilize neuronal cAMP levels, 2) siRNA bound to the cationic shell targeting RhoA, an intracellular signaling molecule activated by multiple neuronal growth inhibitors, and 3) a monoclonal antibody against the Nogo receptor (mNgR1) that binds MAIs for neuronal targeting and inhibition of MAI/receptor binding. The Specific Aims are: 1. to synthesize and evaluate PgP- mNgR1 nanoparticles as a drug and siRNA carrier, 2. to evaluate the ability of PgP-mNgR1 nanotherapeutics loaded with rolipram and RhoA siRNA to inhibit RhoA expression, elevate cAMP, and stimulate neurite outgrowth on inhibitory substrates, and 3. to evaluate neuroplasticity and functional recovery in response to delivery of nanotherapeutics in a rat direct cortical impact model of TBI. These studies will rely upon close collaboration with the Cell, Tissue, and Molecular Analysis Core and Bioengineering and Bioimaging Core for material characterization, analysis of cell response, and animal imaging and on the expertise of the PI's mentors Drs. Mark Kindy and Michael Lynn in basic and clinical neuroscience. Through these studies, we will develop PgP as a targeted, combinatorial drug-delivery system capable of addressing the complex pathology of TBI. Due to their modular design, these NPs can be modified for use with various drugs/siRNA and targeting ligands, providing broad applicability to a diverse range of pathologies.